1. Field of the Invention
The present invention relates to a liquid discharging method to discharge the required amount of a liquid by the bubble generated by applying the thermal energy to the liquid as well as a liquid discharging head, a head cartridge and a liquid discharging device.
2. Related Background Art
A conventional ink jet recording method, so-called a bubble jet recording method is well known which causes the status change of ink with sudden volume change (bubble generation) by applying such pulse energy as heat pulse etc., to ink according to a signal to be recorded to discharge ink from an ink discharging port by a pressure caused by such status change in order to apply ink onto a record medium. As disclosed in U.S. Pat. No. 4,723,129, a recording device using the above-mentioned bubble jet recording method generally comprises an ink discharging port, an ink flow path connected with such ink discharging port, an electrothermal converting element as a means for generating energy to discharge ink provided in the ink flow path.
It is possible to record an image of high quality at a high speed with low noise by this recording method. At the same time, the ink discharging ports can be arranged in high density on a recording head for such recording method. Therefore, the bubble jet recording method has many advantages. For example, an image of high resolution and even a color image can be recorded by means of a compact equipment. For this reason, the bubble jet recording method has been recently applied not only to various kinds of office apparatus such as a printer, a copying machine, and a facsimile, but also to industrial systems such as a textile printing machine.
With the diffusion of bubble jet technology into various fields as described above, in recent years, the following developments have been made:
For example, a heat generating element has been optimized by adjusting the thickness of a protective film to improve energy efficiency. This improvement is effective to enhance the heat transfer efficiency to a liquid such as ink. On the other hand, a driving condition for discharging a liquid such as ink properly at a high speed with stable bubble generation to obtain a high quality image has been proposed. An improved flow path shape has also been proposed to obtain a liquid discharging head with high refilling speed to fill a liquid flow path with a liquid after a liquid discharging process in order to achieve high speed recording.
Various flow path shapes have been proposed, as described above. Japanese Patent Application Laid-Open No. 63-199972 discloses a flow path construction shown in FIGS. 36A and 36B. The invention disclosed in the patent is the flow path construction and head manufacturing process based on back wave due to bubble generation (a pressure in a direction opposite to a liquid discharging port, that is, a pressure toward a liquid chamber 12). The back wave is known as an opposite energy because it is not the energy in the liquid discharging direction.
In the case of the flow path construction shown in FIGS. 36A and 36B, a valve 10 is installed at a location on a side opposite to the liquid discharging port 11 with respect to the heat generating element 2, apart from the bubble generating region of the heat generating element. The valve 10 is manufactured from a plate, etc. As shown in FIG. 36B, it has an initial position on the ceiling of the flow path 3. When the bubble generates, it droops into the flow path 3. In the case of the invention shown FIGS. 36A and 36B, the valve 10 controls part of the back wave to check the movement of the back wave toward an upstream side. As a result, an energy loss is controlled. However, the careful examination of the bubble generating process reveals that the control of part of the back wave by the valve 10 installed in the flow path 3 containing a liquid to be discharged is not preferable for the liquid discharging process. That is, originally, the back wave itself does not have a direct influence on the liquid discharging process as described above. When the back wave generates in the flow path 3, as shown in FIG. 36A, a pressure having a direct influence on the liquid discharging process can discharge a liquid from the flow path 3. Therefore, the control of the back wave, especially the control of part of the back wave does not have a great influence on the liquid discharging process.
On the other hand, in the case of the bubble jet recording method, due to the repetition of the heating process under the condition that the heat generating element is in contact with ink, burned ink may accumulate on the surface of the heat generating element. Some kind of ink leaves much burned ink and results in unstable bubble generation. As a result, smooth ink discharge is not guaranteed. Therefore, the development of a process to discharge a liquid smoothly without denaturing it has been eagerly waited, even through a liquid to be discharged is apt to deteriorate and even though such liquid does not generate sufficient bubble.
Japanese Patent Application Laid-Open Nos. 61-69467, 55-81172 and U.S. Pat. No. 4,480,259, etc., disclose a process in which two kinds of liquid, namely, a bubble-generating liquid and a liquid to be discharged (a discharging liquid) are employed separately to discharge the latter by giving the bubble pressure to the latter. In the case of these inventions, ink, the liquid to be discharged is completely separated from the bubbling liquid by means of a flexible membrane made of silicone rubber, etc. so that the former does not come into contact with the latter, and at the same time the pressure due to bubble generation is transmitted to the liquid to be discharged by the displacement of the flexible membrane. By such configuration, the accumulation of burned liquid on the surface of the heat generating element can be prevented and the liquid to be discharged can be more freely selected.
However, in the case of the above-mentioned head configuration in which the liquid to be discharged is completely separated from the bubbling liquid, the pressure due to bubble generation is transmitted to the liquid to be discharged by the expansion/contraction and the displacement of the flexible membrane, so the considerable portion of such pressure is absorbed by such membrane. In addition, the flexible membrane does not displace much, so an advantage due to the separation of the liquid to be discharged from the bubbling liquid can be obtained, but the energy efficiency and the liquid discharging pressure may lower.
Some inventors of the present invention made the following analyses to provide a novel liquid discharging method using the bubble as well as a head, etc. for such method based on the principle of a liquid droplet discharging process: the first technical analysis to analyze the principle of the mechanism of a movable member in a flow path based on its behavior; the second analysis to analyze the principle of the droplet discharge by the bubble pressure; the third analysis to analyze the bubble generating region of a heat generating element. As a result, it becomes possible to improve the basic discharging properties of the liquid discharging method by the bubble (the bubble due to film boiling) generated in the flow path to such high level not expected from the conventional viewpoint.
The present applicant has established an entirely novel method for controlling the bubble actively by arranging the fulcrum of the movable member on the upstream side and its free end on the discharging port side, namely, on the downstream side, and at the same time by arranging the movable member itself in the heat generating element area or the bubble generating area based on the results of the above-mentioned analyses. The present applicant has applied such method to be patented. More particularly, it was found out that the bubble discharging properties could be greatly improved by the growing portion of the bubble generated in the downstream side, taking the energy of the bubble itself for the liquid discharging amount into consideration. It was also found out that the above-mentioned bubble has the greatest influences on the liquid discharging properties. In other words, the liquid discharging efficiency and the liquid discharging speed can be improved by efficiently directing such growing bubble portion toward the liquid discharging direction. The method in accordance with the present invention achieves very high technical level compared with the conventional liquid discharging method by positively moving the growing portion of the bubble in the downstream side to the free end of the movable member. In the case of the present invention, it is preferable to investigate the structural factors of the movable member, the flow path, etc., relating to the bubble generation on the downstream side from a center line of the heat generating region, for example, an area in the flowing direction of the liquid passing through a electrothermal converting element or on the downstream side from a center line of the bubble generating surface area. On the other hand, a liquid refilling speed can be greatly improved by modifying the arrangement of the movable member and the structure of a liquid supply path.
U.S. Pat. No. 5,821,962 to Kudo et al. shows a liquid ejecting head for ejecting liquid by generation of a bubble. The head includes an ejection outlet through which the liquid is ejected, a liquid flow path in fluid communication with the ejection outlet, a bubble generation region for generating the bubble in the liquid and a moveable member disposed opposite to the bubble generation region. The head is provided with a base portion wherein the moveable member is displaced by pressure produced upon bubble generation to eject the liquid through the ejection outlet. Kudo et al. however, do not disclose any particular relationship between the applied discharge energy and the discharge volume; and Kudo et al. do not disclose how to use such relationship to stabilize the amount of liquid ejected.
As described above, the present invention is directed to the liquid discharging method and the liquid discharging head in which the bubble generating direction is concentrated on the downstream side by arranging the movable member in a direction opposite to the bubble generating region in the liquid path. The present invention aims at the improvement of liquid discharging efficiency and stability by improved liquid discharging principle to use the bubble energy more effectively by modifying the structure of the movable member and the flow path. The present invention also aims at the achievement of surprisingly stable liquid discharging performance by discovering a novel liquid discharging amount control means. The principal objects of the present invention are as follows:
It is the first object of the present invention to provide a liquid discharging method and a liquid discharging head in which the volume in a space from a liquid discharging port to the free end of a movable member is controlled as the liquid amount to be discharged.
It is the second object of the present invention to provide a liquid discharging method and a liquid discharging head in which discharging performance is more stable by applying the liquid discharging energy higher than that required for discharging the liquid amount to be discharged from the liquid discharging port to the free end of the movable member.
It is the third object of the present invention to provide a liquid discharging method and a liquid discharging head in which meniscus refilling speed after a liquid droplet discharging process is enhanced.
It is the fourth object of the present invention to provide a novel liquid discharging principle by controlling the generated bubble drastically.
It is the fifth object of the present invention to provide a liquid discharging method and a liquid discharging head, etc., in which the liquid can be discharged smoothly by enhancing the liquid discharging efficiency and the liquid discharging pressure and by reducing the heat accumulated in the liquid on the heat generating element and at the same time by decreasing remaining bubble on the heat generating element.
It is the sixth object of the present invention to provide a liquid discharging head, etc., in which liquid refilling frequency is increased and the printing speed, etc., is improved by decreasing the inertia in a direction opposite to the liquid supply direction due to the back wave and at the same time by reducing meniscus backward motion by means of the valve function of the movable member.
It is the seventh object of the present invention to provide a liquid discharging method and a liquid discharging head, etc., with sufficiently high liquid discharging efficiency and liquid discharging pressure in which the accumulation of burned liquid on the heat generating element can be reduced and by which the applications of the liquid to be discharged can he extended.
It is the eighth object of the present invention to provide a liquid discharging method and a liquid discharging head, etc., in which the kind of the liquid to be discharged can be more freely selected.
It is the ninth object of the present invention to provide a liquid discharging head and device which can be easily manufactured at low cost by constructing a liquid introduction path for supplying a plurality of liquids with less parts and to provide a compact liquid discharging head, device, etc.
In the case of the above-mentioned liquid discharging head equipped with a movable member in a flow path in accordance with the present invention which discharges the liquid droplets out of the liquid discharging port by displacing such movable member by the bubble generated in the bubble generating region, more stable liquid discharging amount and more high speed liquid refilling properties can be achieved by limiting the liquid discharging amount to a certain level when the energy applied for discharging the liquid reaches a certain value and by discharging the liquid in such limited domain. The typical requirements to achieve the above-mentioned purposes are as follows:
The liquid discharging method in accordance with the present invention employs the liquid discharging head consisting of the liquid discharging port; the bubble generating region where the bubble generates in the liquid; and the movable member which can move between a first position and a second position which is located at a point farther from the bubble generating region compared with the first position. In this liquid discharging head, the movable member moves from the first position to the second position by the pressure of the bubble generated by the bubble generating energy in the bubble generating region. At the same time, the bubble expands farther toward the downstream direction compared with the upstream direction by the displacement of the movable member. Under this condition, the liquid is discharged out of the liquid discharging port by the liquid discharging energy applied to such liquid. In this case, the movable member has its free end in the downstream side with respect to its fulcrum, and the amount of the liquid to be discharged out of the liquid discharging port is controlled by the liquid discharging energy contained in the saturation domain to be saturated in accordance with the increase of such energy.
Alternately, the liquid discharging method in accordance with the present invention employs the liquid discharging head consisting of the liquid discharging port; a first liquid flow path connected with the liquid discharging port; a second liquid flow path including the bubble generating region; and the movable member equipped with its free end in the side of the liquid discharging port and located between the first liquid flow path and the bubble generating region. In this liquid discharging head, the free end of the movable member moves toward the first liquid flow path by the pressure of the bubble generated by the bubble generating energy in the bubble generating region. Under this condition, the liquid is discharged out of the liquid discharging port by the liquid discharging energy applied to such liquid by introducing the pressure due to the displacement of the movable member. The amount of the liquid to be discharged out of the liquid discharging port is controlled by the liquid discharging head according to the energy contained in the saturation domain to be saturated in accordance with the increase of such energy.
Alternately, the liquid discharging method in accordance with the present invention supplies the liquid from the upstream side of the heat generating element along such element located in the liquid flow path; generates the bubble by heating the liquid with the heat generated by the heat generating element activated by the bubble generating energy; displaces the free end of the movable member which is equipped with such free end on the liquid discharging port side and faces the heat generating element by the pressure of the bubble generated; and discharges the liquid out of the liquid discharging port by applying the liquid discharging energy to the liquid by introducing the pressure due to the displacement of the movable member into the liquid discharging port side. Under this condition, the liquid is discharged in a domain where the amount of the liquid to be discharged out of the liquid discharging port is substantially saturated with the increase of the liquid discharging energy.
Alternately, the liquid discharging method in accordance with the present invention employs the movable member equipped with its displaceable free end on the liquid discharging port side; displaces the movable member by the bubble including at least a pressure component directly acting on the liquid droplet discharging operation, after causing film boiling by applying the bubble generating energy to the liquid; and discharges the liquid out of the liquid discharging port by applying the liquid discharging energy to the liquid by introducing the bubble including the pressure component into the liquid discharging port side. Under this condition, the liquid is discharged by applying the liquid discharging energy corresponding to the domain where the amount of the liquid to be discharged out of the liquid discharging port is substantially saturated with the increase of the liquid discharging energy.
Alternately, the liquid discharging method in accordance with the present invention in which the liquid droplets are discharged out of the liquid discharging port situated on the downstream side of the bubble generating side with respect to the liquid droplet discharging direction in a direction not opposite to the bubble generating region by the bubble generated by the bubble generating energy in the bubble generating region. The above-mentioned liquid discharging method employs the movable member equipped with the free end which seals the liquid discharging port side domain of the bubble generating region from the liquid discharging port, and equipped with a surface ranging from the fulcrum situated on the side opposite to the liquid discharging port with respect to the free end. The above-mentioned liquid discharging method discharges the liquid by opening the bubble generating region to the liquid discharging port by moving the substantially sealed free end, and by applying the liquid droplet discharging pressure to the liquid. Under this condition, the liquid is discharged by applying the liquid discharging energy corresponding to the domain where the amount of the liquid to be discharged out of the liquid discharging port is substantially saturated with the increase of the liquid discharging energy.
Alternately, the liquid discharging head consists of the liquid discharging port; the bubble generating region where the bubble generates in the liquid; and the movable member which is arranged in the bubble generating region and can move between a first position and a second position which is located at a point farther from the bubble generating region compared with the first position. In this liquid discharging head, the movable member moves from the first position to the second position by the pressure of the bubble generated by the bubble generating pulse energy in the bubble generating region. At the same time, the bubble expands further toward the downstream direction compared with the upstream direction by the displacement of the movable member. In this case, the liquid is discharged out of the liquid discharging port by the liquid discharging energy applied to such liquid. Under this condition, the liquid is discharged by applying the liquid discharging energy corresponding to the domain where the amount of the liquid to be discharged out of the liquid discharging port is substantially saturated with the increase of the liquid discharging energy.
Alternately, the liquid discharging head consists of a first liquid flow path connected with the liquid discharging port; a second liquid flow path including the bubble generating region where the bubble generate in the liquid with the heat applied to the liquid by the bubble generating energy; and the movable member equipped with its free end on the side of the liquid discharging port and located between the first liquid flow path and the bubble generating region. In this liquid discharging head, the liquid is discharged by moving the free end of the movable member toward the first liquid flow path by the pressure of the bubble generated in the bubble generating region, and by applying the bubble generating energy to the liquid by introducing the pressure to the liquid discharging port side of the first liquid flow path. Under this condition, the amount of the liquid to be discharged out of the liquid discharging port is substantially saturated with the increase of the liquid discharging energy.
Alternately, the liquid discharging head in accordance with the present invention consists of the liquid discharging port; the liquid flow path including the heat generating element for generating the bubble in the liquid by heating the liquid and a liquid supply path for supplying the heat generating element with the liquid from the upstream side of the heat generating element along such element; the movable member having its free end on the liquid discharging port side and facing the heat generating element and introducing the pressure into the liquid discharging port by displacing the free end by the pressure of the bubble generated. When the liquid is discharged out of the liquid discharging port by the liquid discharging energy from the heat generating element, the amount of the liquid to be discharged out of the orifice is substantially saturated with the increase of the liquid discharging energy.
Alternately, the liquid discharging head in accordance with the present invention consists of the liquid discharging port; the heat generating element for generating the bubble in the liquid by heating the liquid; the movable member having its free end on the liquid discharging port side and facing the heat generating element and introducing the pressure into the liquid discharging port side by displacing the free end by the pressure of the bubble generated; and the liquid supply path for supplying the heat generating element with the liquid from the upstream side along the surface near to the heat generating element. When the liquid is discharged out of the liquid discharging port by the liquid discharging energy from the heat generating element, the amount of the liquid to be discharged out of the liquid discharging port is substantially saturated with the increase of the liquid discharging energy.
Alternately, the liquid discharging head in accordance with the present invention consists of a plurality of the liquid discharging ports; plurality of grooves for forming a plurality of first liquid flow paths connects directly with each corresponding liquid discharging port; grooved member including concave portion forming first common liquid chamber for supplying a plurality of the first liquid flow paths above-mentioned with the liquid; an element substrate including a plurality of heat generating elements for generating the bubble in the liquid by heating it; a separation wall which is situated between the grooved element and the element substrate, constitutes a part of the wall of second liquid flow path corresponding to the heat generating elements and includes the movable member situated at a position facing the heat generating elements and displaceable toward the first liquid flow path by the bubble pressure. When the liquid is discharged out of the liquid discharging port by the liquid discharging energy from the heat generating element, the amount of the liquid to be discharged out of the liquid discharging port is substantially saturated with the increase of the liquid discharging energy.
Alternately, the liquid discharging head cartridge in accordance with the present invention consists of the liquid discharging head and a liquid container for containing the liquid to be supplied to the liquid discharging head.
Alternately, the liquid discharging device in accordance with the present invention consists of the liquid discharging head and a driving signal supply means for supplying a driving signal to discharge the liquid out of the liquid discharging head.
Alternately, the liquid discharging device in accordance with the present invention consists of the liquid discharging head and a recording medium transport means for transporting such recording medium to receive the liquid discharged out of the liquid discharging head.
According to the liquid discharging method, liquid discharging head, etc., of the present invention, the liquid discharging efficiency is improved by the synergetic effects of the bubble generated and the movable member displaceable by such bubble. At the same time, both very stable liquid discharging amount and more speedy liquid refilling properties can be obtained by discharging the liquid in a domain where the amount of the liquid to be discharged out of the liquid discharging port is saturated with the increase of the liquid discharging energy. As a result, stable bubble generation and stable liquid droplet formation can be achieved, and at the same time a high quality image can be recorded at a high speed by discharging the liquid at a rapid speed. The resulting image has very high quality with very slight variation and unevenness in its density because the variation of the liquid discharging amount due to the environmental changes and the uneven properties inherent for the head is very slight.
The other advantages of the present invention will be understood more clearly with reference to the following description of the preferred embodiments of the present invention.
The terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d in the present patent specification are used with respect to direction in which the liquid flows from the liquid supply source to the liquid discharging port through the bubble generating region (or the movable member) and the direction opposite to such direction respectively.
The xe2x80x9cdownstream sidexe2x80x9d with respect to the bubble itself chiefly means the bubble discharging port side directly relating to the liquid droplet discharging process. More particularly, such term means the downstream side of the central portion of the bubble in the liquid flow direction and in the configuration arrangement and a domain on the downstream side of the centerline of the heat generating element.
The term xe2x80x9csubstantial sealingxe2x80x9d means the condition that the bubble cannot pass through a slit around the movable member before the displacement of the movable member during a bubble growing process.
The term xe2x80x9cseparation wallxe2x80x9d means in a broad sense a wall (which may include the movable member) for separating the bubble generating region and an area directly communicating with the liquid discharging port, and in a narrow sense a wall which separates the liquid flow path containing the bubble generating region from the liquid flow path directly communicating with the liquid discharging port to prevent mixing of the liquids in the liquid flow paths.
The term xe2x80x9cdisplacement trace of the free end of the movable memberxe2x80x9d means an arc-like face drawn by the displacement of the movable member around its fulcrum. If such arc is small, it can be regarded as a flat surface.
The term xe2x80x9csubstantially saturated saturation domainxe2x80x9d of the liquid discharging amount means an area including a perfect saturation area in which the liquid discharging area So (xcexcm2) of the liquid discharging face multiplied by a distance OE (xcexcm) from the liquid discharging face to the displacement trace, or track surface drawn by the free end of the movable member, as well as an area from a inflection point at which the curve leaves a domain where the liquid discharging amount is proportional to effective bubble generating area to such perfect saturation area. The above-mentioned inflection point changes slightly according to the liquid conditions, head discharging port shape or the area changes near to the liquid discharging port. However, it can be represented by 0.9Soxc2x7OE in a range less than 150 xcexcm for the liquid discharging head. This inflection point is the physical pulling-back component to pull back the liquid which is being drawn back during the liquid discharging process. It corresponds to the pulling-back force around the liquid discharging port. It can be regarded as (2xcfx80Rxc3x971 xcexcm) at the maximum. Therefore, the substantial saturation area containing the inflection point is expressed as (Soxe2x88x922xcfx80R)xc3x97OE.
The term xe2x80x9crecordingxe2x80x9d means a process for forming a meaningful image such as a character, and figure on a recording means and a process for forming a meaningless image such as a pattern.